Fluid-blast circuit interrupter with delayed moving contact travel

ABSTRACT

A fluid-blast circuit interrupter is provided having a pair of separable contacts, the moving contact of which has two delayed periods during its opening travel, the first of which is during the time of increasing fluid pressure resulting from pistongenerating action, with a relatively short arc length, and the second delayed period of the movable contact is during the time of fluid flow with an arc length of greater length adequate for arc interruption. Subsequently, the moving contact is further withdrawn to the fully open-circuit position to thereby be capable of withstanding the returning recovery-voltage transient.

United States Patent Roidt et al.

[54] FLUID-BLAST CIRCUIT INTERRUPT ER WITH DELAYED MOVING CONTACT TRAVEL Inventors:

both of Pittsburgh, Pa.

[451 Apr. 25, 1972 Primary Examiner-Robert S. Macon Att0rneyA. T. Stratton, C. L. McI-Iale and W. R. Crout Assignee: Westinghouse Electric Corporation, Pittsburgh, Pa. [57] ABSTRACT Filed: Mar. 6, 1970 A fluid-blast circuit interrupter is provided having a pair of separable contacts, the moving contact of which has two PP 17,198 delayed periods during its opening travel, the first of which is during the time of increasing fluid pressure resulting from piston-generating action, with a relatively short arc length, Cl "200/148 200/148 A and the second delayed period of the movable contact is dur- Int. Cl. ..H0lh 33/70 ing the time f fl id fl with an arc length f greater length Fi f Search 148 148 adequate for are interruption. Subsequently, the moving con- 200/153 tact is further withdrawn to the fully open-circuit position to thereby be capable of withstanding the returning recoveryvoltage transient.

6 Claims, 9 Drawing Figures 3p 33 22 \I A i1 35 22--r T '1.4

2 61: 31 26 312 zsq P'A'TE'N'TEDAPR 25 I912 3, s59 O65 SHEET 1 0F 4 WITNESSES k B a N L ATTORNEY FLUID-BLAST CIRCUIT INTERRUPTER WITH DELAYED MOVING CONTACT TRAVEL CROSS-REFERENCES TO RELATED APPLICATIONS Reference may be made to U.S. Pat. application filed July 31, I967, Ser. No. 657,122, now U.S. Pat. No. 3,588,407, issued June 29, 1971 to Russell E. Frink and Stanislaw A. Milianowicz, entitled Delayed-Blast F luid-Flow Circuit Interrupter, and to U.S. Pat. application filed Jan. 8, 1968, Ser. No. 696,415, by Stanislaw A. Milianowicz, entitled Fluid- Blast Circuit Interrupter With Insulating Arc Shield, both of the aforesaid patent applications being assigned to the assignee of the instant application.

BACKGROUND OF THE INVENTION It is common practice in the art of fluid-blast circuit interrupters in which a movable piston is utilized, to associate the movement of the piston with the movable contact structure, so that the two move simultaneously together. This has the general drawback, or disadvantage that the arc is considerably lengthened during the time of the buildup of pressure by the piston, and thereby creates an increasing opposing arc-voltage and arc-pressure. The resulting back-pressure tends to halt, or otherwise impede, the working motion of the movable piston, which is attempting to generate adequate fluid pressure. An example of such piston devices are those set forth in the aforesaid two patent applications, in which the piston motion is positively connected to the motion of the movable contact.

SUMMARY OF THE INVENTION In accordance with a preferred embodiment of the present invention, there is provided a fluid-blast circuit interrupter of the movable piston type, in which the movable contact has an independent motion, as contrasted with the movement of the movable piston. This is achieved, according to the present invention, by a means, such as a cam having a cam shape, such that the movable contact has two delayed periods, or dwell periods, during its opening movement, the first of which occurs during the buildup of fluid pressure by piston action, and the second delayed period is during the time of arcing, at which the arc is maintained at a desired minimum length, and receives the full effect of the cumulative increased pistongenerated fluid blast.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a perspective view of a three-pole circuit interrupter embodying the principles of the present invention;

FIG. 2 is a considerably-enlarged longitudinal sectional view taken through one of the pole-units of FIG. I, the contact structure being illustrated in the closed-circuit position;

FIGS. 3 and 4 fragmentarily illustrate the separation of the contact structure at different distances, and illustrating the two delayed periods;

FIG. 5 illustrates the fully open-circuit position of the movable contact structure;

FIGS. 6 and 7 illustrate sectional views taken through the circuit interrupter along the lines VlVI and VII-VII, respectively, of FIGS. 2 and 5; and,

FIGS. 8 and 9 illustrate details of the cam operation.

DESCRIPTION OF THE PREFERREDEMBODIMENT Referring to the drawings, and more particularly to FIG. 1 thereof, the reference numeral 1 generally designates a threepole fluid-blast circuit interrupter comprising three spaced pole assemblies A, 8" and C." As will be apparent from FIG. 1, each pole-assembly includes, generally, an upper end plate 2, a generally upstanding cylindrical housing 3, and a lower end plate and mechanism housing 4. Disposed exteriorly of the mechanism housing 4 is a drive-crank 5, affixed to an operating shaft 6, and a generally horizontally reciprocally movable insulating operating rod 7 is pivotally secured to the external operating crank 5, as at 8, and is connected to a drive-crank 9 through a pivotal connection 10. The three drive-cranks 9, only one of which is shown, are affixed and rotatable with an operating drive-shaft 11, which is connected to a suitable mechanism 12, which constitutes no part of the present invention, and may be of the type set forth in U.S. Pat. No. 3,183,332, issued May ll, 1965 to Russell E. Frink and Paul Olsson, and assigned to the assignee of the present invention.

It will be apparent from FIG. 1 that a suitable supporting grounded framework 14 is utilized comprising vertical channel members 15 with interbracing structural steel members 16, having horizontally extending insulating support straps 16b secured thereto, which assist in supporting the interrupting assemblies. Additionally, lower insulator supports 17 may be employed extending generally horizontally from a channel support member 16c, the latter being affixed to the vertical support channels 15.

FIGS. 2, 6 and 7 more clearly illustrate the internal construction of each of the interrupting assemblies. With reference to FIG. 2, it will be noted that there is provided the cylindrical housing 3 of a suitable insulating material having at one end thereof the end closure plate 2 having a line-terminal connection 2a constituting an integral part thereof. At the opposite end of the tubular housing 3 is the operating casting 4, within which extends the rotatable operating shaft 6 having affixed thereto, as by a key pin 18, an internally disposed operating crank 19, the latter being pivotally connected, as at 20, to a pair of metallic operating links 21. The upper ends of the operating links 21, as viewed in FIGS. 2, 3 and 5, are pivotally connected to a pivot pin 22, the latter extending through apertures 23 provided in a spider-like actuator 24, which is fastened, to the end 26a of a movable operating cylinder 26 having a closed-end plate portion 26b.

The movable contact structure 29 of the puffer-type circuit interrupter, as shown more clearly in FIG. 2, comprises the movable piston cylinder 26 having an annular piston-driving portion 26b, which has its working travel within a compression chamber 31, and generates fluid within this chamber 31 to move through the ducts 32 provided in the insulating nozzle 33 and force fluid into the arc 34 (FIG. 4). A movable contact 35 engages the stationary contact fingers 30 in the closed position of FIG. 2. It has a follower operating rod 38 with a follower roller 40 to follow the cam surface 360 of a rotatable cam 36.

According to the present invention, the movable contact 35 has two delayed periods, the first of which is illustrated in FIG. 3 of the drawings. As shown in FIG. 3, the arc 34 established is of minimum length, and the pressure is being built up during this time within the compression chamber 31. During this first dwell time transient pressure surges associated with the striking of the arc are allowed to decay and hence, to prevent transient back pressures upon the piston.

FIG. 4 illustrates the second position of the are 34, at which time it is receiving the full blasting effect from the pistongenerated fluid pressure.

According to the present invention, the movement of the movable contact 35 is independent of the motion of the annular driving piston 26b and the piston cylinder 26. This is achieved by the cam 36, which is fixedly secured to, and movable with, the operating shaft 6 extending laterally out of the lower mechanism housing 4. As shown more clearly in FIGS. 2 and 9, the cam 36 has a configured surface 360, such that the movable contact 35, biased toward a closed'position by a compression spring 37, nevertheless must follow the contour of the cam surface 360, and thereby is compelled to have two delaying positions, as illustrated in FIGS. 3 and 4 of the drawings.

As illustrated in FIG. 2, the operating shaft 6 has a pair of spaced crank-arms 19a, 19b affixed thereto, and movable therewith, the outer free ends of which are pivotally secured, as at 20, to a pair of floating metallic links 21, which are pivotally connected to the movable spider member 24, thereby actuating the operating piston cylinder 26.

- open position of the interrupter.

The advantage of the present invention results from the fact that the independent motion of the movable venting contact 35 assures a buildup of adequate fluid pressure by maintaining the arc 34 during this time at a minimum length, as illustrated in FIG. 3. The arc voltage and arc-generated pressure is consequently at a minimum during this time.

When the fluid pressure is adequate, as shown in FIG. 4, at this time the cam contour 36a is such as to pick up the movable contact 35 and move it to its second delayed position, as shown in H6. 4. In this position, as illustrated in FIG. 4, the are 34 is receiving the full impact of the radially inwardly directed fluid pressure to bring about fast arc extinction.

FIG. 2 illustrates, to an enlarged scale, the cam contour 36a and the several legends indicate the positions of the movable contact 35 during the rotation of the cam 36. As shown, the fluid is exhausted through the movable tubular contact 35 and also through a tubular stationary arcing contact 43. A valve plate 46 closes during the working stroke of the annular piston 26b, and opens during the closing travel of the piston to facilitate contact closing.

From the foregoing description, it will be apparent that there has been provided an improved fluid-blast circuit interrupter, in which independent motion of the movable contact 35 permits two delaying periods, while the continuous piston motion 26b generates continuously an ever-increasing fluidblast pressure. The time-delay periods are such that the are 34 moves from its minimum position to its interrupting position at a time, when the fluid pressure is adequate to completely assure its instant extinction.

We claim as our invention:

1. A fluid-blast piston-type circuit interrupter including, in combination:

a. separable contact means including a pair of cooperable contacts, at least one of which is movable and the other relatively stationary;

b. operating means for the circuit interrupter effective to cause the movable contact to assume two consecutive open delaying arcing positions one of short arc length and the other of longer arc length;

c. said operating means causing continuous fluid-increasing pressure by said piston means during both of said consecutive open delaying arcing positions of the movable contact;

(1. the first delaying position occurring when the established arc is of short length incapable of being interrupted by the then-available fluid pressure; and,

e. the second delaying position occurring when the arc is of a length capable of being interrupted by the then-available fluid pressure.

2. The fluid-blast circuit interrupter of claim 1, wherein the motion of the movable contact is achieved by the use of a suitably-configured cam.

3. The fluid-blast circuit interrupter of claim 1, wherein the piston means includes a movable operating piston cylinder linked to an operating shaft, and a cam fixedly secured to said operating shaft and causing the independent motion of the movable contact.

4. The fluid-blast circuit interrupter of claim 2, wherein the cam is positioned between two floating links operating the piston means.

5. A piston-type of fluid-blast circuit interrupter including, in combination:

a. a relatively stationary venting contact cooperable with a movable venting contact to establish an arc;

b. a movable piston structure for forcing generated fluid pressure toward the established are including a movable piston;

c. operating means for causing continuous working travel of the iston during the opening operation;

d. sai operating means including means for causing two delayed positions of the movable venting contact;

e. said first delayed position assuring a short arc length during buildup of piston-generated fluid pressure;

i". said second delayed position assuring adequate arc length at a time when adequate fluid pressure force has been attained; and,

g. fluid-directing means to cause radially inwardly directed fluid pressure to exhaust in substantially opposite directions through both cooperable venting contacts.

6. The combination of claim 5, wherein the movable contact is spring-biased to the closed position, and the operating means includes a suitably configured cam to independently control the motion of the movable venting contact. 

1. A fluid-blast piston-type circuit interrupter including, in combination: a. separable contact means including a pair of cooperable contacts, at least one of which is movable and the other relatively stationary; b. operating means for the circuit interrupter effective to cause the movable contact to assume two consecutive open delaying arcing positions one of short arc length and the other of longer arc length; c. said operating means causing continuous fluid-increasing pressure by said piston means during both of said consecutive open delaying arcing positions of the movable contact; d. the first delaying position occurring when the established Arc is of short length incapable of being interrupted by the then-available fluid pressure; and, e. the second delaying position occurring when the arc is of a length capable of being interrupted by the then-available fluid pressure.
 2. The fluid-blast circuit interrupter of claim 1, wherein the motion of the movable contact is achieved by the use of a suitably-configured cam.
 3. The fluid-blast circuit interrupter of claim 1, wherein the piston means includes a movable operating piston cylinder linked to an operating shaft, and a cam fixedly secured to said operating shaft and causing the independent motion of the movable contact.
 4. The fluid-blast circuit interrupter of claim 2, wherein the cam is positioned between two floating links operating the piston means.
 5. A piston-type of fluid-blast circuit interrupter including, in combination: a. a relatively stationary venting contact cooperable with a movable venting contact to establish an arc; b. a movable piston structure for forcing generated fluid pressure toward the established arc including a movable piston; c. operating means for causing continuous working travel of the piston during the opening operation; d. said operating means including means for causing two delayed positions of the movable venting contact; e. said first delayed position assuring a short arc length during buildup of piston-generated fluid pressure; f. said second delayed position assuring adequate arc length at a time when adequate fluid pressure force has been attained; and, g. fluid-directing means to cause radially inwardly directed fluid pressure to exhaust in substantially opposite directions through both cooperable venting contacts.
 6. The combination of claim 5, wherein the movable contact is spring-biased to the closed position, and the operating means includes a suitably configured cam to independently control the motion of the movable venting contact. 